The present invention relates to an energetic plasticizer used in an insensitive high performance explosive and a propellant, and a preparation method thereof.
Bis (2,2-dinitropropyl) formal (BDNPF) is a potent plasticizer used in an insensitive high performance explosive and propellant. However, it has an inherent disadvantage that it is solid at room temperature such that it can not be independently used. Thus, as a plasticizer, an eutectic mixture of BDNPF with its homologue is used.
U.S. Pat. No. 5,648,556 disclosed a plasticizer comprising an eutectic mixture of BDNPF/A, bis(2,2-dinitropropyl) formal/acetal, in which BDNPA keeps BDNPF from crystallizing out. The plasticizer comprising an eutectic mixture of BDNPF/A has been commercially available and wildly used in an explosive and a propellant. But, it is well known that thermal/chemical stability of an acetal group in the BDNPA is lower than that of the formal group in the BDNPF.
U.S. Pat. No. 4,997,499 disclosed a 2-components mixed-formal, BDNPF and 2,2-dinitropropyl 2,2-dinitrobutyl formal (DNPBF), in which DNPBF was used as an inhibitor of crystallization of BDNPF. The 2-components mixed-formal is obtained by reacting a mixture of 2,2-dinitropropanol and 2,2-dinitrobutanol with formaldehyde, but it is also known that about 10% of bis(2,2-dinitropropyl) diformal is always produced as an unfavorable side product.
The 2-components mixed-formal is believed to be superior to the BDNPF/A in terms of the thermal and chemical properties and cost involved. Nevertheless, it has never been realized in the formulation of an explosive and a propellant. It is expected that this is resulted from the difficulty of process, additional synthesis of 2,2-dinitrobutanol, the reduction of the energy efficiency.
Therefore, an object of the present invention is to provide an improved energetic plasticizer having excellent thermal and chemical properties as well as being economic.
Another object of the present invention is to provide a method for preparing the plasticizer.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an energetic plasticizer comprising eutectic mixture of bis(2,2-dinitropropyl) formal (BDNPF) and bis(2,2-dinitropropyl) diformal (BDNPDF), wherein BDNPDF keeps BDNPF from crystallizing out.
The present invention relates to an energetic plasticizer comprising eutectic mixture of bis(2,2-dinitropropyl) formal (BDNPF) and a material that keeps BDNPF from crystallizing out, wherein the material that keeps BDNPF from crystallizing out is bis(2,2-dinitropropyl) diformal (BDNPDF). More specifically, the present invention relates to an energetic plasticizer comprising eutectic mixture of BDNPF and BDNPDF, wherein the BDNPDF keeps BDNPF from crystallizing out. The amount of BDNPDF used in the energetic plasticizer is preferably in the range of 8xcx9c44% by mole, based on the mixture of BDNPF and BDNPDF. The amount of BDNPF used in the energetic plasticizer is preferably in the range of 92xcx9c56% by mole, based on the mixture of BDNPF and BDNPDF.
The plasticizer of the present invention can be achieved by suitably adjusting the amount of the formaldehyde with which 2,2-dinitropropanol is reacted to form a reaction mixture comprising BDNPF and BDNPDF. More specifically, it can be achieved by slowly adding a concentrated sulfuric acid solution to a solution in which 2,2-dinitropropanol and 1xcx9c3 equivalent of paraformaldehyde or s-trioxane is dissolved in methylene chloride, wherein the methylene chloride solution is maintained at a temperature of xe2x88x9230xcx9c20xc2x0 C., extracting mixed formals from the obtained reaction mixture, and purifying the mixed formals.
Reaction of 2,2-dinitropropanol with formaldehyde is shown in scheme 1:
The plasticizer of the present invention in which BDNPDF prevents BDNPF from crystallizing out is not crystallized even though it stands at the temperature xe2x88x9220xc2x0 C. for more than 6 months, while its thermal and chemical properties are similar to that of conventional plasticizer. Also, by using BDNPDF, that has been considered as a by-product, as an inhibitor of crystallization, no additional process is required to remove BDNPDF. Moreover, the cost involved is lower.